Reaction of Acetals and α,β-Unsaturated Ethers

Hoaglin, R. I.; Hirsh, D. H.

doi:10.1021/ja01178a061

Cited by 76 publications

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“…Among various procedures described − for the synthesis of this requisite aldehyde 7 , few offer both low cost and effectiveness at a multigram level. Regarding these criterions, the condensation of acetals with enol-ethers (the Müller-Cunradi/Pieroh process), , followed by hydrolysis of the resulting 1,1,3-trialkoxyalkanes, seemed suitable. Quite surprisingly, this scheme seemed not to have been already applied to the synthesis of 7 .…”

Section: Resultsmentioning

confidence: 99%

Regioselective Synthesis and Diels−Alder Reaction of 3,4-Dimethylpenta-1,3-diene. Conformational Study of Bicyclic Adducts Structures by ¹H NMR (NOESY, ASIS) and Molecular Modeling (MM2, AM1, RHF, and DFT)

et al. 1999

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A three-step, regioselective synthesis of 3,4-dimethylpenta-1,3-diene 1 has been developed. The condensation of acetone diethylacetal with ethyl propenyl ether yielded, after hydrolysis of the resulting triethoxy adduct 10, 2,3-dimethyl-2-butenal 7. Wittig reaction of 7 with methylenetriphenylphosphorane afforded desired diene 1 in 31% overall yield, easily scalable to the 10 g level. Diels−Alder reaction of 1 with maleic anhydride in benzene was known to afford a 50:50 mixture of “normal” (2) and “rearranged” (3) adducts. In THF as solvent, 2 has been reproducibly obtained in over 90% yield as a 98:2 mixture with 3. 1H NMR spectroscopy (NOESY, ASIS) and molecular modeling (MM2, AM1, ab initio) have been used jointly to determine the conformation of 2 and 3. All are consistent with a folded structure of “rearranged” 3. On the other hand, only RHF/6-31G* and B3LYP/6-31G* ab initio models were in agreement with NMR spectroscopy for an extended conformation of adduct 2. In this case, neither MM2 nor AM1 models gave results consistent with NMR: discrepancies as high as 30° were noted for some dihedrals between these models and ab initio ones.

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Section: Resultsmentioning

confidence: 99%

Regioselective Synthesis and Diels−Alder Reaction of 3,4-Dimethylpenta-1,3-diene. Conformational Study of Bicyclic Adducts Structures by ¹H NMR (NOESY, ASIS) and Molecular Modeling (MM2, AM1, RHF, and DFT)

et al. 1999

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“…Reaction of 3 with 2.5 equiv of dihydrocinnamaldehyde in the presence of BF 3 ·OEt 2 and 2,6-di- tert -butylpyridine (2,6-DTBP) at −78 °C led to the unexpected product 4 in 82% yield, Table , entry 1. The Mukaiyama aldol reaction has taken place but the oxocarbenium ion, rather than cyclizing onto the alkene, added a second equivalent of the aldehyde to produce the 1,3-dioxane structure 4 . Compound 4 was not the desired product, but it was formed very cleanly.…”

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confidence: 99%

Titanium(IV)-Promoted Mukaiyama Aldol−Prins Cyclizations

2003

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[reaction: see text] A new version of the Mukaiyama aldol-Prins (MAP) cyclization has been developed. Unsaturated enol ethers such as 3 were found to couple with aldehydes in the presence of TiBr(4) to give 4-bromotetrahydropyran products. This cascade reaction sequence leads to the formation of two new carbon-carbon bonds, a ring, and three new stereogenic centers. We expect this reaction to be a powerful new tool in synthesis.

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“…An advantage of our new methodology is that the acetals 13 are inactive toward competitive addition to enol ethers: in all the cases we used acetal and vinyl ether in equimolar ratio and did not observe the formation of any secondary addition products, while previously described reactions of stoichiometric amounts of acetals and enol ethers led to the formation of oligomers. , This difference in the reactivity patterns in acetals and 11 becomes crucial as far as their reactions with cyclic enol ethers are concerned. Substituted tetrahydrofurans and tetrahydropyrans are the structural subunits in naturally occurring polyether antibiotics, pheromones, etc . , Additions of acetals to dihydrofurans and dihydropyrans were previously found to yield the corresponding 2-alkoxy-3-(α-alkoxy)alkyltetrahydrofurans or -pyrans; 5,12,13 however, these reactions are often complicated by the formation of secondary condensation products.…”

Section: Introductionmentioning

confidence: 87%

Lewis Acid-Catalyzed Additions of (Benzotriazol-1-yl)diethoxymethane to Enol Ethers and Enamides. New Syntheses of β-Alkoxyalkanal and β-Aminoalkanal Acetals

et al. 1997

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Addition of (benzotriazol-1-yl)diethoxymethane 11 to various acyclic and cyclic enol ethers and enamides produces the corresponding adducts, which were reacted with either NaAlH(4) or Grignard reagents to afford acyclic acetal-ethers (18a-f), cyclic alpha-(substituted)-beta-acetals (19a-c), amino-acetals (24a,b), and 1,3-amino-ethers (25), all known but previously difficult-to-access classes of compounds.

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Reaction of Acetals and α,β-Unsaturated Ethers

Cited by 76 publications

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Regioselective Synthesis and Diels−Alder Reaction of 3,4-Dimethylpenta-1,3-diene. Conformational Study of Bicyclic Adducts Structures by ¹H NMR (NOESY, ASIS) and Molecular Modeling (MM2, AM1, RHF, and DFT)

Regioselective Synthesis and Diels−Alder Reaction of 3,4-Dimethylpenta-1,3-diene. Conformational Study of Bicyclic Adducts Structures by ¹H NMR (NOESY, ASIS) and Molecular Modeling (MM2, AM1, RHF, and DFT)

Titanium(IV)-Promoted Mukaiyama Aldol−Prins Cyclizations

Lewis Acid-Catalyzed Additions of (Benzotriazol-1-yl)diethoxymethane to Enol Ethers and Enamides. New Syntheses of β-Alkoxyalkanal and β-Aminoalkanal Acetals

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Reaction of Acetals and α,β-Unsaturated Ethers

Cited by 76 publications

References 0 publications

Regioselective Synthesis and Diels−Alder Reaction of 3,4-Dimethylpenta-1,3-diene. Conformational Study of Bicyclic Adducts Structures by 1H NMR (NOESY, ASIS) and Molecular Modeling (MM2, AM1, RHF, and DFT)

Regioselective Synthesis and Diels−Alder Reaction of 3,4-Dimethylpenta-1,3-diene. Conformational Study of Bicyclic Adducts Structures by 1H NMR (NOESY, ASIS) and Molecular Modeling (MM2, AM1, RHF, and DFT)

Titanium(IV)-Promoted Mukaiyama Aldol−Prins Cyclizations

Lewis Acid-Catalyzed Additions of (Benzotriazol-1-yl)diethoxymethane to Enol Ethers and Enamides. New Syntheses of β-Alkoxyalkanal and β-Aminoalkanal Acetals

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Regioselective Synthesis and Diels−Alder Reaction of 3,4-Dimethylpenta-1,3-diene. Conformational Study of Bicyclic Adducts Structures by ¹H NMR (NOESY, ASIS) and Molecular Modeling (MM2, AM1, RHF, and DFT)

Regioselective Synthesis and Diels−Alder Reaction of 3,4-Dimethylpenta-1,3-diene. Conformational Study of Bicyclic Adducts Structures by ¹H NMR (NOESY, ASIS) and Molecular Modeling (MM2, AM1, RHF, and DFT)